SECTION 5. Engine operation details
For these reasons, it is very useful to use a convex combination of these relationships as the throttle curve
to avoid the RPM or thrust to react too sensitively to the throttle position at either end of the range.
Assuming the throttle position is mapped to
[
0
,
1
]
such that
off
corresponds to 0 and
full
corresponds to 1,
we get the target relative RPM function as
r
:
[
0
,
1
]
→
[
0
,
1
]
,
r
(
s
) = (
1
−
c
1
)
s
+
c
1
3
√
s
.
(1)
As our throttle position will only be between
idle
and off, we need the linear mapping
τ
:
[
0
,
1
]
−
>
[
0
,
1
]
,
τ
(
t
)
:
=
at
+
b
,
(2)
with
b
:
=
RPM
idle
RPM
f ull
,
a
:
= (
1
+
b
)
−
1
.
Now we can get the true RPM as a function of the relative throttle position
t
∈
[
0
,
1
]
, where 0 corresponds
to
neutral
and 1 corresponds to
full
R
:
[
0
,
1
]
→
[
0
,
1
]
,
R
(
t
) =
RPM
idle
+
r
◦
τ
(
t
)(
RPM
f ull
−
RPM
idle
)
.
(3)
This way,
R
(
0
) =
RPM
idle
,
R
(
1
) =
RPM
f ull
and
R
is a convex combination of a linear function and a root
function in between.
(a) Relative rpm over relative throttle for differ-
ent values of
c
1
.
(b) Relative thrust over relative throttle for dif-
ferent values of
c
1
.
These convex combinations (the grey and black lines corresponding to
c
1
=
0
.
3 and
c
1
=
0
.
7 in Figures 4a,
4b) result in throttle curves that are easier to control at both low and high RPM.
5.3
Autostart
The autostart sequence can be triggered when the engine is in
standby
mode. The sequence is as follows (with
statuses as given on the GSU, also see Table 1).
1.
BURNER ON
: The glow plug is switched on for 8
s
. The starter slowly increases the engine’s RPM.
2.
FUEL IGNIT
: Modulation of the starter fuel valve and starting of the fuel pump. Upon successful fuel
ignition (exhaust temperature exceeds 150
◦
C), transition to
FUEL HEAT
.
3.
FUEL HEAT
: Transition from ignition to main line fuel supply. The burner is still supplied with fuel while
the main fuel line valve is opened. The starter’s voltage (and thus the RPM) is increased slowly.
4.
RAMP UP
: The engine’s RPM is increased by increasing the main fuel line’s flow rate. The starter and
burner are switched off at the configured RPM, respectively.
After the completion of the autostart sequence, the engine is running at idle RPM. If a H
ORNET
-III with
analogue (brushed) pump is used, the ECU will then execute the auto calibration (Section 5.4). If a H
ORNET
-
III-ClubSport is used, the engine will be in automatic mode (see Section 5.5) and ready to go!
18